The basis for uplink (UL) and downlink (DL) scheduling is dynamic scheduling. In a long term evolution (LTE) wireless communication system, scheduling information is transmitted during transmission timing intervals (TTIs) to a wireless transmit/receive unit (WTRU) via a physical downlink control channel (PDCCH). It has been agreed by radio access network (RAN) working groups (i.e., RAN2) to support semi-persistent scheduling for the DL and the UL in LTE. For semi-persistently scheduled WTRUs in a TTI, a DL/UL grant does not need to be sent for initial data transmission. The only exception is when an evolved Node-B (eNB) wants to override the persistent resource assignment, which by definition should be infrequent. Otherwise, the sole purpose of a DL/UL persistent resource assignment is lost. As an optimization for voice over Internet protocol (VoIP), persistent scheduling is used for both DL and UL, where the resource for the initial transmissions is persistently allocated and the resources for the hybrid automatic repeat request (HARQ) retransmissions is dynamically allocated.
Persistent resource scheduling is configured and controlled, (e.g., turned on and off), by radio resource control (RRC) signaling. For instance, persistent resource scheduling may be controlled based on the periodicity of a resource allocation. HARQ processes that are used for persistent scheduling are provided using RRC signaling.
The exact timing, resources, and transport format parameters used for a persistent DL assignment are sent on a layer 1 (L1)/layer 2 (L2) control channel as a normal DL assignment. For example, an HARQ process identification (ID) may be used to indicate that the assignment should be stored. If the persistent DL assignment is missed, which occurs when there is no acknowledgment or non-acknowledgment (NACK), then an evolved Node-B (eNB) resends the assignment.
For VoIP service, the release of semi-persistent resources in both the DL and UL is important. Both explicit resource release and implicit resource release have been previously discussed, but there has yet to be a decision made as to the implementation of these features.
Furthermore, there is a need to clarify potential new signalings to support the release of a persistent resource using both explicit and implicit methods, procedures for either explicit or implicit persistent resource release, a failure case handling when persistent resource release signaling is lost or corrupted, new signaling for the activation of the persistent resource, and new signalings for the reconfiguration of the persistent resource allocation.
There exists the need for new signalings and rules for the activation, deactivation, reconfiguration, and release of UL and DL persistent resources in LTE systems.